1. Field of the Invention
This invention relates generally to lathe attachments and more specifically to such attachments having an axially movable chuck.
2. Description of the Prior Art
Machine tools, such as lathes, and their fixtures are well known in the art. Some examples are shown in U.S. Pat. No. 879,741 by H.L. Coit; U.S. Pat. No. 933,179 by A.I. Jacobs; U.S. Pat. No. 1,150,142 by A.P. Morrow; U.S. Pat. No. 1,195,214 by O.D. Hapgood; U.S. Pat. No. 3,691,883 by M.S. Ingram; U.S. Pat. No. 4,021,051 by Y. Toyomoto, et al; U.S. Pat. No. 4,379,667 by H. Yoshimoto, et al; U.S. Pat. No. 4,496,163 by K.G. Bernfeld; and U.S. Pat. No. 4,548,532 by K. Watanabe, et al.
In a lathe, the piece to be worked upon is held in a chuck which rotates. A tool, such as a drill, is held in a chuck or a tailstock turret of a tailstock. The tailstock is moved axially toward the rotating work to engage the tool to the piece. This axial movement of the tailstock and tool is typically accomplished by using a hand crank and screw assembly. There are some difficulties with this method. The heavy tailstock and frictional forces in the hand crank assembly can make movement of the hand crank awkward for the lathe operator. A skilled lathe operator must be able to feel how much force the tool is exerting on the work piece. This is especially critical in precision drilling situations which involve using drill bits of very small size. If the lathe operator advances the drill too fast, the drill will not have time to clear the drill shavings away and the drill will break. However, the heavy tailstock and hand crank assembly interfere with the lathe operator's ability to feel how much force the small drill is exerting on the workpiece.
One prior art attempt to solve these problems uses a slidable lathe attachment. The attachment is mounted in the chuck of a tailstock. The attachment has a rod which slides axially foward from a housing. A chuck is attached to the end of the rod for holding a drill bit. The operator is able to slide the drill forward without moving the tailstock. Yet, this attachment is difficult to use because the exact position of the drill bit is hard to control. The drill bit can be easily broken if too much force is applied. In addition, because the attachment is itself mounted in a chuck, there can be misalignment problems.